Bicycles, tricycles and other pedaled vehicles are some of the most popular items with children and adults alike. Although such pedaled vehicles have been in existence for a very long time, these vehicles remain as popular and relevant today as in the past. Accordingly, manufacturers continue to strive to improve all aspects of these vehicles. By way of example, manufacturers continually strive to improve the assembly, maintenance, and aesthetics of pedaled vehicles.
For example, one aspect of current bicycle design for which improvement is sought is with the assembly and the replacement of the chain. FIG. 1 illustrates a conventional drive system for a bicycle 10 which includes a front sprocket 12 operatively coupled to a crank (not shown), a rear sprocket 14 operatively coupled to the rear wheel (not shown), and a chain 16 extending therebetween for transmitting the power from the rider acting on the crank to the rear wheel to thereby propel the bicycle 10 in a certain direction. As is illustrated in FIG. 1, it is generally known that the chain 16 forms a closed loop about the bicycle frame 18, such as chain stay 20, for example, such that the chain 16 cannot simply be removed from the bicycle 10 (even if the rear wheel is removed from the bicycle). In other words, some portion of the frame 18 is on the inside or interior of the closed-loop chain 16 that prevents the chain 16 from being assembled to or removed from the bicycle 10 in a closed-loop configuration. The inventor has noted that this is due to the fact that the rear sprocket 14 is generally on the inside of the frame 18 (e.g., between the two chain stays), the front sprocket 12 is generally on the outside of the frame 18, and the upper and lower portions 22, 24 of the chain 16 cross from outside the frame 18 to inside the frame 18 on opposite sides of the chain stay 20. More particularly, the lower portion 24 of the chain 16 crosses from outside the frame 18 to inside the frame 18 at a location generally below the chain stay 20 while the upper portion 22 of the chain 16 crosses from outside the frame 18 to inside the frame 18 at a location generally above the chain stay 20. This arrangement results in a closed loop configuration of the chain 16 about the chain stay 20.
In any event, the closed-loop configuration of the chain 16 around the frame 18 has several consequences. In regard to chain assembly, during the initial assembly process, a specified amount of chain is extracted from a chain roll or spool and cut to length. The chain is then wrapped around the front and rear sprockets and coupled together to form this closed-loop configuration. This chain assembly process is typically manual and is therefore labor intensive and costly. Secondly, as the process is not conducive to automation, there may be inconsistencies in chain length, which may result in quality assurance concerns.
In regard to chain replacement, the chain must be designed in a manner that allows the closed-loop configuration of the chain 16 to be selectively broken (e.g., so as to have two ends) and re-established. To this end, the chain 16 may include a master link (not shown), which is specially designed to allow the chain to be broken and re-established from a closed-loop configuration. However, the drawback to this design is that the master link represents a weak link in the chain which may operate as a potential failure site for chain breakage. Alternatively, the chain may include moveable link pins, one of which may be nearly removed (but preferably not completely removed) from the chain so as to release the chain from its closed-loop configuration. The drawbacks to this approach are that a special tool is required to disengage the selected link pin and that many consumers are simply unaware of this method of removing the chain. In any event, chain repair or replacement often results in a trip to a local bicycle shop, which may be inconvenient to the consumer and incur unwanted costs.
Current bicycle drive systems have additional drawbacks as well. For example, the lower portion 24 of the chain path may be close to or adjacent the riding surface of the bicycle (e.g., road, trail, track, etc.). Accordingly, due to the proximity of this portion of the chain to the riding surface, the chain 16 may pick up a significant amount of dirt, grease, or other debris that negatively impacts the performance of the chain 16, thereby potentially introducing power transmission losses. Furthermore, in some countries or regions, various regulations may require that a chain guard (not shown) be provided to cover at least a portion of the chain, such as the front sprocket 12 and the upper chain portion 22. Moreover, in certain countries or regions, regulations may require that the chain guard cover both the upper and lower chain portions. In current drive systems, wherein the upper and lower chain portions 22, 24 may be spaced apart by a significant amount, this may require relatively large chain guards, which may increase overall costs of the bicycle. Additionally, some believe that current drive systems are aesthetically flawed, appearing bulky and unwieldy due to the relatively large spacing between the upper and lower chain portions 22, 24 and the awkward, non-parallel lines the chain makes in combination with the frame 18.
Accordingly, there is a need for an improved drive system for a pedaled vehicle, such as a bicycle, that permits the chain or other power transmitting element to be assembled or replaced on the vehicle without breaking and/or re-establishing the closed-loop configuration of the element. There is also a need for an improved drive system that reduces the amount of debris exposed to the chain or power transmitting element, reduces the size of the chain guard, and provides enhanced aesthetics.